First, the function of each segment of the plastic recycling machine

plastic recycling machine output is closely related to the structure of the plastic recycling machine, at present, the most widely used extrusion theory is based on the three basic functions of conveying, melting and metering. Thus a common screw consists of three segments; feeding segment, compression segment and a homogenization segment. The charging section is for solids conveying, the compression section is for plastic melting and compression, and the homogenization section is for homogenization and metering.

In the charging section, the plastic is an unplasticized solid, and its solid transport is based on the solid transport theory, the core of which is the friction theory of solids, in which the solid transport rate is related to the friction coefficient (fb) between the material and the surface of the screw and the friction coefficient (f) between the material and the surface of the barrel, when fb>f. When fb>f, the solid transport rate can be improved.

In the compression section, the plastic gradually changes from a solid state to a viscous flow state, and the mixing, shearing and frictional effects in this section are more complicated. In the 1960s, the phase migration theory of the compression section emerged, which is based on thermodynamics and can be calculated more accurately, but the derivation of the calculation process is complicated.

The main function of the homogenization section is to increase the pressure of the molten plastic delivered from the compression section, further homogenize it, and make it extrude from the die opening with constant pressure and quantity. The melt transport theory of the homogenizing section is based on fluid mechanics, and the rheological state, productivity and power consumption of the homogenizing section have been studied and calculated in more detail.

Second, the material flow condition in the machine simple

Plastic in the homogenization section for viscous flow state, due to the head mouth mold resistance and other factors caused by the pressure difference along the screw direction seems to be and the barrel screw thread gap between the outer surface, its flow conditions are as follows.

① positive flow, that is, along the screw groove flow to the head.

② counter-flow, also known as counter-flow, is caused by the head, manifold, filter, etc. on the melt counter-flow, its flow direction is opposite to the positive flow.

⑧ Trailing flow, also known as cross-flow, is the circulation of the melt in the screw groove, this flow has little effect on the total extrusion volume and can be neglected. However, it has great influence on the mixing, heat exchange and plasticization of the melt.

④Leakage flow.

Third, the main factors affecting the output

(1) the impact of force-extrusion volume with the increase in head pressure and a linear decline.

① for the screw groove deep and short screw plastic recycling machine, extrusion volume with the increase in head pressure and a sharp decline.

②Increase the temperature of the die opening, the extrusion volume is slowed down by the influence of the head pressure.

③When the die resistance is high (small effective load area), the extrusion volume is more influenced by the head pressure.

④When the screw speed is high, the extrusion volume is high, but the increase in the head pressure is proportional to the decrease in the extrusion volume.

⑤ The larger the screw L/D ratio, the less the extrusion volume is affected by the head pressure.

⑥The extrusion volume of the uncooled screw is much more influenced by the head pressure than that of the cooled screw.

(7) the larger the clearance between the screw and the barrel, the greater the proportion of the extruded volume decreases with the increase in head pressure

(2) The effect of screw speed – extrusion volume increases with the increase of screw speed, but it is not a linear relationship.

① HDPE>LDPE>PP.

②The extrusion volume of low-viscosity molten material is more influenced by the screw speed.

③The extrusion volume increases with the increase of screw rotational speed at high melt temperature. But at low melt temperatures, the increase is very slight.

④The extrusion volume of an uncooled screw is slightly more influenced by screw speed than that of cooled screw.

⑤The extruded volume increases with the increase of screw speed when the mouth die resistance is low; on the contrary, its increase is very small.

(3)The extrusion volume increases rapidly with the increase of material melt index.

(4) The extrusion volume increases with the increase of the length of homogenization section.

(5) When the head pressure is low, the extruding volume increases with the deepening of the screw groove of the homogenizing section; but if the head pressure is high, the extruding volume decreases with the deepening of the screw groove of the homogenizing section.

(6) The extrusion volume decreases with the increase of the gap between the screw and the barrel. But when the clearance is greater than 1mm, the extrusion volume decreases significantly.

(7) The extrusion volume decreases with the increase of temperature in the charging section.

(8) With the increase of melting temperature, the extruded volume does not change at the beginning, and when the temperature continues to increase to a certain degree and the material viscosity decreases, the extruded volume decreases rapidly.

(9)When the barrel temperature is raised to a certain limit, the extruded volume also decreases sharply due to the rapid decrease of material viscosity.

(10)The extrusion volume decreases with the increase of volatiles in the material.

(11) The extruded volume decreases sharply with the increase of screw temperature.

(12) With the deepening of the screw groove, the extrusion volume increases rapidly at the beginning, and then decreases sharply when it reaches a certain limit. This is because the depth of the screw groove increases, the degree of plasticization of the material in the screw becomes worse.

(13) The extrusion volume increases proportionally with the increase of the area of the forming hole of the mouth die.

(14) extrusion volume with the increase in the length of the flat flow part of the mouth die and proportionally decreased.

Fourth, the application of the factors affecting the output of plastic recycling machine

(1) Different melt flow rate of the material, can not be compared according to the screw speed of the lift out volume.

(2) extrusion volume and screw speed is not proportional to the relationship.

(3) Even if the same model of plastic recycling machine (screw structure is the same, the temperature setting of each section is the same). Because the length of the adapter, the head mouth area, filter resistance, the degree of screw cooling, the material preheating temperature differences. As well as the plastic recycling machine itself screw and barrel clearance of the small difference, etc., extrusion of the same material when the extrusion volume is not the same.

(4) For the fixed plastic recycling machine, the extrusion volume will be different at different times, influenced by the melt pressure, screw temperature and the stability of the material.

The above are the influencing factors and applications of plastic recycling machine output.